In a conventional electrophotographic copying machine, only one straight elongated linear tubular lamp is used for illuminating an original to be copied. The light image of the original can be transferred to a photosensitive member by scanning the tubular lamp with a scanning mirror under a platen on which the original is placed. The lamps most frequently used have such arrangement that a plurality of filaments for illumination are suspended in the tube with a predetermined equal space and the respective filaments are connected in series. In the copying machine using only one tubular lamp of the type as described above, if one of the filaments is cut, the copying machine can not be used.
In the technical field to which the present invention pertains, it has been considered that only such elongated lamp could be used and the lamp should illuminate over the entire width of the platen simultaneously. However, according to the technical knowledge of the present inventors, there is no reason to illuminate the over all width of the platform for all kinds of size of an original.